Automated or robotic self-propelled swimming pool cleaners traditionally contact and move about on the pool surfaces being cleaned on axle-mounted wheels or on endless tracks that are powered by a separate drive motor through a gear train. The wheels or tracks are aligned with the longitudinal axis of the cleaner. Swimming pool cleaning robots that move on wheels generally have two electric motors, a pump motor that provides power to a water pump that is used to dislodge and/or vacuum debris up into a filter, and a drive motor which is used to propel the robot over the surfaces of the pool that are to be cleaned. The drive motor can be connected through a gear train directly to one or more wheels or axles, or through a belt and pulleys to propel the cleaner; or to a water pump, which can be external to the robotic cleaner that produces a pressurized stream, or water jet, that moves the cleaning apparatus by reactive force or by driving a water turbine connected via a gear train to the wheels or endless track. The movement of the pool cleaners of the prior art, when powered by either the turbine or the direct or reactive jet is in one direction and the movement is random.
Control of the longitudinal directional movement of the pool cleaner can be accomplished by elaborate electronic circuitry, as is the case when stepper and D.C. brushless motors are employed. Other control systems enable the cleaner to climb the vertical sidewall of the pool until a portion of the cleaner extends above the waterline and/or the unit has moved laterally along the sidewall, after which the motor drive reverses and the cleaner returns to the bottom surface of the pool along a different path. The water-powered cleaners of the prior art also rely on the reorientation of the cleaner while in contact with the wall to effect a random change in direction. However, under certain circumstances, it is a waste of time and energy, and produces unnecessary wear and tear to have the robotic cleaner climb the sidewall solely for purpose of changing the direction of movement of the cleaner.
It has also been proposed to direct the scanning movement of a pool cleaner mechanically by use of a three-wheeled array in which the third wheel is mounted centrally and opposite the other pair of wheels, and the axle upon which the third wheel is mounted is able to rotate in a horizontal plane around a vertical axis. A so-called free-wheeling version of this apparatus is shown on U.S. Pat. No. 3,979,788.
In U.S. Pat. No. 3,229,315, the third wheel is mounted in a plate and the plate is engaged by a gear mechanism that positively rotates the horizontal axle and determines the directional changes in the orientation of the third wheel.
It is also known in the prior art to provide a pool cleaner with a vertical plunger or piston that can be moved by a hydraulic force into contact with the bottom of the pool to cause the cleaner to pivot and change direction. The timing must be controlled by a pre-programmed integrated circuit (“IC”) device.
It is also known from U.S. Pat. No. 4,348,192 to equip the feed water hose of a circular floating pool cleaning device with a continuous discharge water jet nozzle that randomly reorients itself to a reversing direction when the forward movement of the floating cleaner is impeded. In addition to the movable water jet discharge nozzle attached to the underside of the floating cleaner, the hose is equipped with a plurality of rearwardly-facing jet nozzles that move the water hose in a random pattern and facilitate movement of the cleaner.
Commercial pool cleaners of the prior art that employ pressurized water to effect random movement have also been equipped with so-called “back-up” valves that periodically interrupt and divert the flow of water to the cleaner and discharge it through a valve that has jets facing upstream, thereby creating a reactive force to move the hose and, perhaps, the attached cleaner in a generally backward direction. The back-up valve can be actuated by the flow of water through a fitting attached to the hose. The movement resulting from the activation of the back-up valve jets is also random and may have no effect on reorienting a cleaner that has become immobilized, e.g., in the corner of the pool or by a ladder or other obstruction.
The apparatus of the prior art for use in propelling and directing the scanning movement of automated robotic pool cleaners is lacking in several important aspects. For example, the present state-of-the-art machines employ pre-programmed, integrated circuit (“IC”) devices that produce a specific predetermined scanning pattern. The design and production of these IC devices is relatively expensive and the scanning patterns produced have been found to be ineffective in pools having irregular configurations and/or obstructions built into their bottoms or sidewalls.
Cleaners propelled by a water jet discharge move only in a generally forward direction, and their movement is random, such randomness being accentuated by equipping the unit with a flexible hose or tail that whips about erratically to alter the direction of the cleaner.
Cleaners equipped with gear trains for driving wheels or endless tracks represent an additional expense in the design, manufacture and assembly of numerous small, precision-fit parts; the owner or operator of the apparatus will also incur the time and expense of maintaining and securing replacement parts due to wear and tear during the life of the machine. A cleaning apparatus constructed with a pivotable third wheel that operates in a random fashion or in accordance with a program has the same drawbacks associated with the production, assembly and maintenance of numerous small moving parts.
The robotic pool cleaners of the prior art are also lacking in mechanical control means for the on-site adjustment of the scanning patterns of the apparatus with respect to the specific configuration of the pool being cleaned.
In U.S. Pat. No. 6,742,613, a self-propelled robotic pool cleaner includes a reversible drive means for propelling the apparatus in opposite directions, which directions correspond generally to the longitudinal axis of the apparatus, and a pair of wheels assembled to each of the opposite longitudinal ends of the cleaner. Each pair of wheels are mounted to transverse axles, which are manually positioned and secured at an angle that is acute to the longitudinal axis of the apparatus when the cleaner is moving in at least one direction. In an embodiment, the axles are mounted in slots formed in the base of the housing, and one or more manually adjustable pins are provided to fix and/or change the range of movement of the axle in the slot. These adjustments allow the operator to customize the pattern based upon the size and/or configuration of the specific pool being cleaned. In this manner, the cleaner moves in a clockwise or counter-clockwise direction until the operator manually adjusts the pin positioning to thereby change the angle of the axle with respect to the longitudinal axle.
European Patent No. EP 1,472,425 discloses a swimming pool cleaner that includes wheels fixedly connected to an axle which is transversely mounted through elongated slots formed in the sidewalls of the cleaner proximate each wheel. The axle is mounted on a central pivot that allows the axle to move forward and backward within the physical constraints of the opposing ends of the elongated slots. A rotating fork having two projections, one on either side of the axle must be manually set to provide different steering paths for the cleaner.
A significant deficiency in the design and operation of the pool cleaners of the prior art is their tendency to become immobilized, e.g., in sharp corners, on steps, or even in the skimmer intake openings at the surface of the pool. In such circumstances, the pool cleaner has limited mobility at best, or is incapable of traversing and cleaning the surface of the pool in a worst case scenario.
Yet another significant deficiency in the design and operation of pool cleaners of the prior art is the entanglement or twisting of the buoyant power cable that provides power from an external power source to the cleaner. In particular, as the cleaner turns during cleaning operations, the floating portion of the power cable can become twisted as it helically winds in a counter-clockwise or clockwise direction. The undesirable twisting or coiling of the power cable shortens the length of the power cable, exerts forces on the cleaner that can oppose the movement of the cleaner, as well as places undesirable stresses on the electrical contacts between the power cable and the cleaner.
Swivel connections have been mounted on the top of the cleaner in an attempt to reduce the coiling of the power cable as the cleaner turns. Unfortunately, the swivel mounts do not always prevent the undesirable coiling of the power cable during the continuous turning of the cleaner.